But what value, in fact, did Culp's/LRT have as anchors? Had either been taken, could Lee have mounted a flank attack off of either? No, Longstreet's Emmittsburg Rd. attack would still have had to succeed (which it nearly did, and by the way, Hood's fateful attack was famously aimed at LRT by Lee/Lonstreet). But you are right, the loss of either would have necessitated the evacuation of Cemetery HIll, Cemetery Ridge. Why? The only advantage I can imagine is spotting the fall of shot, since the Union position was well defined, and the holding of LRT could not have deterred the reinforcement of Cemetery Ridge... it might have prevented Pickett's charge.

Guide Tony DeLacy has some excellent discussions of events on ANV held Benner's Hill, which were devastated by concentrated Union fire on the Second Day.

Clearly this was the enveloping position intended to converge fire on E. Cemetery Hill with that from Oak Hill and Seminary Ridge, but it suffered from being less elevated than Union artillery on E. Cemetery and Stevens' Knoll, below Culp's. Taking Culp's would have made these ANV guns much more effective in counterbattery fire concentrated on E. Cemetery Hill, and leveraging the Benner's position probably depended on using Culp's as an easily readable fire observation platform.

Indiviidual gun shot adjustment, in the modern sense, would not have been possible at Gettysburg, but clearly ranging fire adjustment would have had a high priority. When facing the elevated Union posiitions on Cemetery Hill and Ridge traverse adjustment might have been useful but range adjustment would have been of the utmost importance. A simple "down 50 yards" would have made a world of difference to Porter Alexander on the third day.

This is what I think made it imperative that the Union hold Little Round Top on Day 2. I cannot think of any other factor which would have made the contests for LRT and Culp's so vital to the eventual outcome. Cemetery Hill was the key to Gettysburg, and Gettysburg was the key to Lee's eventual success or failure. C.